The announcement by nuclear negotiator Ali Agha Mohammadi came shortly after Iran's new ultra-conservative President Mahmood Ahmadinejad took office.

"I hope to remove the seals and resume activities today," nuclear negotiator Ali Agha Mohammadi told reporters, refering to seals placed by international nuclear inspectors on the conversion plant in the central city of Isfahan.

The European Union and United States on Tuesday issued sharp warnings to Tehran over its threats to resume the sensitive nuclear fuel work, a move that could risk Iran being hauled before the UN Security Council for possible sanctions.

Iran had told the International Atomic Energy Agency on Monday that it planned imminently to resume uranium ore conversion, the first step in the cycle to producing fuel for nuclear reactors, and not wait for a package of trade and other incentives the EU plans to present to Tehran this coming Sunday.

The Europeans have warned that their negotiations, which began late last year, would be halted if Iran ends a freeze on conversion work.